Such ways are especially for take-off and landing runways for aircraft but also roadways for road traffic. The roadways for street traffic are mostly expressways. The ways and corresponding methods are used for renewing existing ways.
Conventional ways have, generally, a conventional construction which comprises a cover layer, a base layer and a frost-protective layer. The cover layer forms the upper end of the traffic surfaces. The cover surfaces are, as a rule, configured to be bonded and comprise concrete or asphalt and, if required, also comprise a pavement covering.
The base layer or base course is essentially responsible for the load bearing capacity of the traffic surface and preferably comprises pebble stones, crushed stone, recycled material or asphalt. Especially under concrete cover layers, base layers are often configured so as to be hydraulically bonded (HGT).
The frost-protective layer serves to ensure a frost secure thickness of the upper structure of the traffic area. A material used here is preferably pebble stones, crushed stone or recycled material.
Further conventional constructions and modifications are set forth, for example, in the RStO 01 (Richtlinien für die Standardisierung des Oberbaus von Verkehrsflächen-derzeitiger Stand 2001) or the “Arbeitshilfen Flugbetriebsflächen” applicable for the German army.
Runways and roadways are subjected to wear over a long load time frame as a consequence of traffic and weather influences. The wear becomes manifest by distressed locations, unevenness and fissures in the upper cover layer. To renew the worn ways, considerable efforts are required and especially the renewing of concrete ways is problematic.
Various methods are known for renewing concrete ways. In a first renewing or renovating method, an additional bituminous cover or topping is applied. For this purpose, the upper lying cover layer is first destressed by crushing the concrete to prevent the later formation of reflection fissures in the bituminous cover. Thereafter, a bituminous cover is applied above the previous way upper surface. Reinforcing fabrics for taking up the stresses occurring in the concrete are rolled in as a supplement in some cases.
Notwithstanding these measures, the penetration of reflection fissures into the asphalt cover can rarely be avoided which, from experience, can be detected already after a few years. This is primarily attributable to concrete pieces which result in different sizes and shapes during the crushing of the concrete cover and which are hardly definable with respect to their physical characteristics. This leads to qualitative and measurable risks.
The high heat absorption of the applied asphalt cover furthermore causes a heating up of the unstressed concrete cover whereby the risk of fissure formation is further increased. This finally leads to a further renewing requirement and puts into question the durability of concrete surface renewal with bituminous covers. Among engineers in the field of road building and runway building, there is therefore considerable reservation with respect to this renewing method notwithstanding the very short construction times.
In practice, replacement new construction is favored as a renewing method and not the least because of the problems of construction cover layers.
Here, the entire configuration of the roadway including the frost layer, the base layer and the concrete cover layer are replaced by a completely new roadway construction. This replacement new construction satisfies all technical requirements but also constitutes, by comparison, the most cost intensive and time intensive renewing method. Furthermore, the tie-up time limit of the concrete, which has to be considered, causes further traffic restrictions which are often not acceptable.
In the journal “Tiefbau-Ingenieurbau-Strassenbau”, 7-8/2006, pages 36 and 37, a new renewing method is introduced which was first applied at the airport in Frankfurt/Main, Germany according to this information. In principle, this method is seen as a replacement new construction. What is significant is that each subzone of 15 m length and 60 m lane width is exchanged in nighttime windows and therefore an unrestricted flight operation during the day is made possible. The concrete cover including the base layer and frost-protective layer disposed therebeneath in a total thickness of 60 cm is removed and is replaced by a fully bonded upper structure of asphalt. This upper structure of asphalt comprises first and second base layers with each base layer having a thickness of 24 cm as well as a binder layer having a thickness of 12 cm.
The cover joint is produced after completion of the binder layer at the end of each work time window in order to make traffic use possible. Because of the thickness of the asphalt packet of 60 cm, the surface temperature is still at approximately 100° C. after placement and must be cooled down to approximately 85° C., possibly with the use of water trucks or the like, to ensure flight operations.
After completing several mutually connected subzones of the runway as described, the top-lying asphalt binder layer of this total thickness is milled down by approximately 4 cm. Directly thereafter, a continuous asphalt cover layer is built-in in the milled-off region which, in turn, defines the final cover top.
The advantage of this renewing method is that the way can be further used during the building time without significant limitations. This renewing method has, however, considerable disadvantages.
Accordingly, the material use of asphalt over the entire top structure of the way is hardly economically justifiable as a rule. Because of compaction, the installation of the individual layers must take place in sublayers of up to 15 cm thickness. This increases the work complexity and limits the area capacity to the comparatively small work subzones of 15 m×60 m.
A further disadvantage is introduced in that individual work subzones, which are to be worked upon, extend over the entire width of the way and for a take-off runway and landing runway can amount to between 30 and 60 m. This is a disadvantage with respect to the expansion of the individual work subzones in the longitudinal direction of the way because the surface capacity is limited to approximately 900 m2 because of time reasons and logistic reasons.
This is especially disadvantageous in the renewing of roadways for street traffic because a complete blocking of the road section to be built and the detouring of the flowing street traffic to other roads is required. This is no longer acceptable for the density of street traffic of today.
Furthermore, because of the shortness of the work sections of 15 m, a relatively high number of work joints results which can become noticeable as jolts for the running traffic during the building phase.
This is especially the case when a transverse profile improvement is undertaken already in the course of the provisional cover closing. This problem can only be solved with the large area cover installation. The relatively high number of work joints can also lead to future problems which applies especially for regions used the most.